Pulverizing apparatus



Feb. 25, 1936.

J. IHLEFELDT PULVERIZING APPARATUS Filed Aug. 20, 1932 a WOM J Patented Feb. 25, 1936 UNITED STATES PATENT OFFICE 2,031,110 PULVERIZING APPARATUS Johannes Ihlefeldt, Dessau, Germany, assignor to the firm G. Polysius, Aktiengesellschafl, Dessau, Germany 6 Claims.

The invention relates to a process for introducing into and discharging currents of gas from tube and compound mills. These currents of gas can be used as well for cooling and ventilating the mill and also for heating it. Although such processes are already known, they are not yet free from difierent defects, or it is only possible, in consequence of the existing grinding conditions, to realize them in practice in a limited way only. In most cases the quantities of air and gas introduced into the mill are very small only, as in consequence of the filling height of the mill loads the entrance and the outlet openings for such currents of gas and air are fixed in their size. This is the reason why in most. cases the quantity of air and gas carried through the mill is not sufficient to attain the desired purpose, that is to say a suflicient cooling and ventilation or heating of the mill.

This inconvenience is removed by the present invention. Whilst up to now the current of gas or air necessary for cooling and ventilating or heating the mill is simply passed through the mill, it is now intended to considerably increase this quantity of air and gas. The current of gas bringing about this cooling and ventilation or heating can for instance be split up into two or more currents, which are introduced into the mill and will leave it partly in countercurrent and partly in equicurrent with the material to be ground. It may be advisable to practice the process in such manner that the quantity of gas of each single part current of gas can be regulated in conformity with the difierent development of heat.

' Such a process for introducing currents of gas into the mill and for discharging them can for instance be accomplished so that the current of gas is introduced at the inlet and at the outlet of the mill and is evacuated towards the centre. One part current of the gas would flow that way in countercurrent and the other in equicurre'nt with the material to be ground through the length of the mill. .Of course, it will also be possible to introduce the current of gas at the centre of the mill and to evacuate it towards the inlet and the outlet. I

By such a process there is realized the very important advantage that at least the double quantity of air can be carried through the mill. The heat to be drawn off is distributed that way to a larger quantity of air and the air is not heated to a. high temperature, so that the transmission of heat is more favourable. On the other hand, there is thus obtained a considerably more efficacious cooling or also heating of the mill, and the conditions for the grinding process are more favourable. The process can also be so carried out that the coarse material at the inlet side of the millis ventilated in equicurrent and 5 the fine material at the outlet side of the mill in countercurrent or vice versa. It is of importance that by the feed of larger quantities of air, as proposed by the invention, the evacuation of heat and consequently the whole grinding process will 10 be improved.

In case of a tube mill, one may feed and 'discharge for instance the current of gas by means of canals or the like, which are in connection with the atmospheric air. In this way the con- 1 tact of the current of gas at the inlet and outlet ports with material to be ground will be avoided. If the process is used at a compound mill, it will be necessary to build canals into the diaphragm for the inlet and outlet of the current of gas, as well as ways for the passage of the material to be ground from one compartment to the other; these canals and ways should be arranged separately from each other. It will thus be possible that the current of gas may enter and escape at the circumference of the mill without contacting with the material flowing to the next grinding compartment.

In order to-efiect this separation of the current of gas from the material, the diaphragm of the compound mills is equipped with a special gas chamber, which regulates the entrance and the escape of the currents of gas towards both sides of the mill as well as towards the circumference of the mill. These gas and air chambers, which regulate the entrance of the currents of gases into the mills and the escape from the mills, are at the same time equipped with tunnelshaped canals, which passthrough the mouths of the gas chamber and which are constructed to provide a smooth passage of the material into the next grinding chamber. Instead of installing these tunnel-shaped canals into the diaphragm for the passage of the material, it would also be possible, not to combine the'gas chamber and the canals with the diaphragm, but to execute them separately from each other. It is expedient to arrange a convenient casing around the openings necessary in the mill shell.

The grits carried away by apart current of gas are again returned to the mill. There are provided for this purpose special pockets, the inlet of which is facing the circumference of the mill, and the outlet of which faces the grinding chamber. In the present example of the invention, the gas chamber, the tunnel-shaped canals for handling the material from one chamber to the other and the pockets for returning the grits are installed in the diaphragm. The regulation or the currents of gas can be effected by special devices, such as throttle valves and the like. These throttle valves can also. be arranged at the inlet and the outlet of the mill.

The enclosed drawing shows an example of application for the use of the process.

Figure 1 shows a longitudinal section of the compound mill,"

Figure 2 shows a part of the longitudinal section of the Figure l, to wit, the section 01' a diaphragm, at which the way of the current of gas is indicated by arrow A,

Figure 3 shows the same view as Figure 2 with indication of the way of the material to be ground from one chamber to the other through the diap agm, Figure4 shows a section along the line aof the Figure 2 and Figure 5 shows a section along the line o-d oi! the Figure 2.

The compound tube mill comprises the mill shell I with inlet 2 and with outlet 3. The mill is subdivided by the diaphragms 4 and 5 into different grinding chambers 6, I and 8. The diaphragm5isshowninFlgures2and3inenlarged scale. It comprises the grate wall 9, the closed wall I0 as well as the separating walls I I and I2 lying between the grate wall 9 and the closed wall III. The diaphragm is enclosed by a casing I3 arranged on the mill shell I; and this casing I3 is preferably joined to the casing I4, which encloses the openings for the entrance and the escape of the currents of gas, which openings are 4 arranged in the mill shell I. At these casings I3 and :4 are arranged the grit returning sockets I5, as shown in Figures 2 and 3.

The space within the separating walls II and I2 forms the gas chamber I6. This chamber regulates the entrance and the oulflet of the currents of gas. If these currents oi! gas enter into the mill at the material inlet and outlet, they meet in the gas chamber I6 as shown by the arrow in Figure 2. Then they pass through the slits 22 into the chamber 23 and from there through the openings 24 arranged in the mill shell I into the casings I3 and I.

If the currents of gas enter Iromthe circumference of the mill, they follow the same path, that is to say from the casings I3 and I4 through the openings of the shell 24, through the chamber 23 and the slits 22 into the gas chamber I6. As shown in Figure 3, thematerial to be ground enters from one grinding compartment I into the other grinding compartment 8 through the gratewall 9, that is to say through the slits 25'arranged in this grate-wall into a preliminary chamber 2t. In order to avoid contact between the current of gas and the material to be ground, the preliminary chamber 26 is connected to a second chamber 28 by means of tunnel-shaped canals 21, which can be seen from Figure 4. The material is here taken by'shovels, which are constructed as air feed canals, and passed through slits 30 by means of a screw 3| to the next grinding compartment.

The grits separated in the gas chamber I6 from the current of gas are introduced into the casing I3 by the rotation of the mill, and by means of the plate 32 they are directed to the rim of shovels. These grits are also separated from the current of gas outside the mill and also handled by chamber l6, thegrits are conveyed through open-' ings 36 to the chamber 28, and from there together with the current of the material to be ground through screw 3| into the next grinding compartment. The'gas chamber I6 is entirely separated from the passage of the material to be ground in consequence of the application of tunnel-shaped canals 21 and pockets 35, so that theair can spread within this chamber without being hindered by the material to be ground. From here it will be evacuated through the canals 23, which also retain the material to be ground from the current of air. The connection of the air socket I4 from the casing I3 ensures by its kidney-shaped form and its slanting flowing-01f surfaces 31 that the air finds an adequate crosssection when flowing through so that every sediment of material is prevented. The casing I3 is sealed at the front walls by convenient sealing devices. Y

For convenience in defining the invention in the appended claims the word gas is employed in its broader sense to include any medium such asair, furnace exhaust gases, or the like, it being understood thatthe specific nature of the gas circulated through the mill constitutes no essentialpart oi the present invention.

I claim:

1. In apparatus of the class described, the combination with a pulverizing mill of elongated form having an inlet for the material to be pulverized adjacent one end and a discharge outlet adjacent the other end, and provided with an apertured partition at an intermediate point to afford separate pulverizing zones, whereby the material may flow generally in one direction through the mill, of means for effecting circulation of gas within the mill in opposite directions in diflerent portions of the length thereof, said means including a port for the gas communicating with the interior of the mill adjacent said partition.

2. In apparatus of the class described, the combination with a pulverizing mill of elongated i'orm having an inlet for the material to be pulverized adjacent one end and a discharge outlet adjacent the other end, whereby the material may flow generally in one direction through the mill, of means for efiecting circulation of gas within the mill in opposite and distinct directions in different portions of the length thereof with respect to a predetermined point intermediate the inlet and outlet of the mill over substantially the entire cross-sectional area of the mill, and means including a port in the mill periphery located at said predetermined point, said means including a device located at said predetermined point and adapted to permit the passage of gas only through said port.

3. In apparatus for pulverizing raw materials, the combination with a pulverizing mill comprising an elongated substantially cylindrical rotatable drum having an inlet for the material to be pulverized adjacent one end and a discharge outlet adjacent the other end, whereby the material may flow generally in one direction through the drum, of means for effecting flow of gas within said drum from each end toward a point intermediate the ends of the drum only, said means including a port in the mill periphery arranged to permit the passage of gas only therethrough,

said port communicating with the interior of the mill intermediate the inlet and outlet thereof and being provided with means to permit the passage of the circulated gas only therethrough.

, 4. In apparatus for pulverizing raw materials, the combination with a pulverizing mill comprising an elongated substantially cylindrical rotatable drum having an inlet for the material to be pulverized adjacent one end and a discharge outlet adjacent the other end, whereby the material may .flow generally in one direction through the drum, of means for efiecting flow of gas within said drum from points intermediate the ends of the drum toward each end thereof only, said means including a port in the mill periphery arranged to permit the passage of gas only therethrough, said port communicating with the interior-of the mill intermediate the inlet and outlet thereof and being'provided with means to permit the passage of the circulated gas only therethrough.

5. In apparatus of the class described, the combination with a pulverizing mill of elongated form having an inlet for the material to be pulverized adjacent one end and a discharge outlet adjacent the other end, whereby the material may flow generally in one direction through the mill, of means for eflecting circulation or gas within the mill in opposite and distinct directions in different portions the length thereof, said means including a port in the mill periphery disposed intermediate the said different portions of the mill and provided with means to permit the passage of gas only therethrough, the direction of flow of gas being the same in each of the said portions of the mill over the entire crosssectional area thereof, and means for effecting independent control of the quantity of gas flowing in either direction.

6. In apparatus of the class described, the combination with a pulverizing mill of elongated form having an inlet for the material to be pulverized adjacent one end and a discharge outlet adjacent the other end, whereby the material may flow generally in one direction through the mill, of means for establishing continuous uni-directional flow of gas in opposite directions between an intermediate point and the ends of the mill, said means-including a port in the mill periphery communicating with the interior of the mill at said intermediate point and provided with means to permit the passage of gas only therethrough.

Jonamms IHLEFELDT. 

